Thus, in the prior art, it is known to stiffen the casing by circumferential stiffeners in order to increase the propagation speed of rotating waves in the casing. Thus, for each number of diameters, the propagation speed of a rotating wave in the casing and the propagation speed of a rotating wave of a bladed wheel become equal only outside the operating range of the turbomachine.
Nevertheless, stiffening the casing can be insufficient or it can lead to adding thicknesses of material on the casing that are unacceptable in terms of the weight requirements that are to be satisfied.